Wireless sensing and controls provides the freedom of device placement and portability/mobility and reduces the cost of installation (no cable placement or drilling required), if the device does not have to be connected to mains power supply. The state-of-the-art power supply solution for wireless, especially for sensors and simple controls, is battery-operated devices. However, the battery has a limited lifetime leading to risk of failure or requiring replacement at a regular scheme, which is resource demanding. The emerging alternative is self-powered devices, which harvest/scavenge the energy required for operation and communication from their surroundings (e.g. light, temperature, movement—e.g. rotation, vibration, flow- or electro-magnetic radiation) or the interaction with the human user/operator.
Especially in the latter case, the focus on optimizing the technical aspects of the design (mechanics, power harvesting, conversion and storage, integration with the load (radio)) to match the amount of energy harvestable from the user action may lead to sacrificing the usability aspects, such as the functionality offered to the user, intuitiveness of controls and ease-of-use of controls (number and order of steps required, esp. compared to the state-of-the-art mains- or battery-powered analogues).
WO-A-01/67580 discloses an electro-mechanical wireless energy harvesting switch as mentioned by way of introduction. This known switch comprises a generator, which preferably is a rotating generator such as an alternator, and it is configured to provide for at least two different control signals in accordance with the operation by a user. Thus in one embodiment the switch comprises two manual actuator members in the form of rocker buttons for optional activation by the user in accordance with the type of control signal the user wants the switch to provide. In another embodiment it comprises a single manual actuator member in the form of a rocker button provided with more e.g. three contacts upon which the user will selectively apply pressure in order to operate the rocker button in accordance with the type of control signal the user wants to provide. A generator activating mechanism, i.e. a mechanical transmission of energy from the user operated rocker button to the generator comprises in a first embodiment a generator activating member and a spring, the generator activating member being movable in a direction against the load of the spring to store energy and being releasable to transfer stored energy to the generator through a generator coupling. For moving the generator activating member against the load of the spring to store energy the generator activating mechanism further comprises a reciprocating rocker arm rotating around an axis and carrying at a free end a spring loaded hinged engagement member engaging the generator activating member in a rest position thereof to push the generator activating member to a loaded position where the engagement member due to contact with a ramp is disengaged from the generator activating member, which is thereby released to return to the rest position transferring energy stored in the spring to the generator. The reciprocating rocker arm and the spring loaded engagement member entail a rather complicated mechanism. Further the arrangement of the reciprocating rocker arm entails a risk of bias and premature wear.
Other examples of electro-mechanical wireless energy harvesting switches are found in EP-A-0 656 612 disclosing a switch in which the generator is activated directly by the action of a user, and U.S. Pat. No. 7,019,241 and EP-A-1 607 993 both of which relates to switches comprising dead-center mechanisms with two rest positions, said switches activating a generator alternately in either direction whenever the switch passes the dead-center while moving from one rest position to another.